# Probing the early-time dynamics of relativistic heavy-ion collisions with electromagnetic radiation

## TL;DR

Electromagnetic radiation in relativistic heavy-ion collisions provides unique insights into early-time dynamics and initial conditions, surpassing hadronic probes in sensitivity to out-of-equilibrium features.

## Contribution

This study demonstrates the heightened sensitivity of electromagnetic probes to initial conditions and out-of-equilibrium states using 3+1D viscous relativistic fluid dynamics.

## Key findings

- Electromagnetic probes are more sensitive to initial conditions than hadronic observables.
- Hadronic observables show limited sensitivity to early-time dynamics.
- Electromagnetic signals access dynamical regions beyond soft hadronic probes.

## Abstract

Using 3+1D viscous relativistic fluid dynamics, we show that electromagnetic probes are sensitive to the initial conditions and to the out-of-equilibrium features of relativistic heavy-ion collisions. Within the same approach, we find that hadronic observables show a much lesser sensitivity to these aspects. We conclude that electromagnetic observables allow access to dynamical regions that are beyond the reach of soft hadronic probes.